According to Michael Dirr's Manual of Woody Landscape Plants, this particular holly is listed as Ilex x Ebony Magic and apparently was discovered in Germany as a natural hybrid. For this reason, the exact parentage is unknown although he indicates it looks to him like possibly I. rugosa crossed with I. aquifolium. The typically recommended male for pollination is Ebony Male. Usually a nursery will stock the various hollies in sets or pairs so your source or another local nursery may have a suitable pollen plant for you next season.